Epidemiological History of Chikungunya Virus

Abstract

Chikungunya virus (CHIKV) is a mosquito-transmitted virus that has been known to cause human disease since 1952 when the virus was first characterized in an outbreak in East Africa. The virus became widely known on a global scale in 2013 when it entered the Western hemisphere and began to move rapidly through 45 counties in under 2 years. Although this expansion was highly visible and on a virtually unprecedented scale, CHIKV actually has a long history of both epidemic and low-level transmission throughout its endemic distribution in Africa and Southeast Asia. The historical epidemiological patterns of CHIKV are different from more recent activity. Apart from a few large outbreaks, activity in Africa has tended to involve only a few human cases at a time that are typically linked to close associations with the enzootic transmission cycle. In contrast, in Asia, where there is no known enzootic cycle, on-going, low-level activity is typical with large periodic urban outbreaks. The epidemiology of CHIKV since its re-emergence in 2004 in coastal Kenya has been characterized by large attack rates, rapid movement and geographic expansion, utilization of alternate mosquito vectors, and adaptation to novel ecologies. Understanding of the historical patterns of the virus as described below provides a framework for appreciating the modern movement of the virus.